Spin and durability improving machine for playing rackets and methods thereof

ABSTRACT

The current invention aims at improving the playability, durability, and spin generation of different playing rackets, as tennis, squash, and badminton rackets. The method to do so is by applying mechanical forces which generate relative motion of the latitudinal strings over the longitudinal strings. This is done in order to create friction that generate depressions in the contact points of the latitudinal strings with the longitudinal strings. These depressions, made by the described method and machine, induce more friction, and generate spin, while increasing the playability and durability during the play.

FIELD OF THE INVENTION

The present invention relates to a machine for improving spin generation and strings durability of playing rackets and the method for making the improved rackets.

BACKGROUND OF THE INVENTION

While playing with playing rackets, such as tennis rackets, the longitudinal strings—defined as those strings which are parallel to the handle, are prone to snapping much more readily than their perpendicular counterpart latitudinal strings, i.e., the latitudinal strings are defined as those perpendicular to the handle. During most shots in play, the magnitude of the projection of the relative velocity of the ball and the contact place with the racket over the latitudinal axis of the racket's plane, i.e., the axis parallel to the latitudinal strings and perpendicular to the longest axis of the racket—the longitudinal axis, is greater than the projection of the same velocity over the longitudinal axis of the racket. That is the reason behind this phenomenon.

When the ball hits the strings, it therefore, pulls the longitudinal strings off their original position. These strings fail to spring back to their initial position while still in contact with the ball, or fail to do so all together. In addition, the friction between longitudinal and latitudinal strings causes an energetic loss. The ball's final spin, after hitting the racket, is determined mostly by the combined forces of the longitudinal strings over the ball. This happens since the ball is mostly hit when the racket's handle is closer to a horizontal position rather than a vertical one. In addition, players usually hit the ball in a closed fashion and force the racket's head upwards during the shot, e.g., closed stance refers to the case where the face of the racket is slightly tilted downwards. The projection of the force, applied by the racket on the ball, in a perpendicular direction to the ball's velocity, applies torque over the ball during the time of interaction, which results in the spinning of the ball.

The friction between the two string types causes the longitudinal strings to wear down quickly. The reason this happens is that the precise points on the longitudinal strings, which are in contact with the latitudinal strings, are being rubbed along several millimeters of the latitudinal strings during each shot. This manner of wearing forms depressions in the rubbing points of the longitudinal strings, shaped by the profile of the latitudinal strings.

Depressions in the longitudinal strings increase the friction with the latitudinal strings, resulting in a further energy loss as heat. Both the hindering of longitudinal strings from retreating back to their initial positions during the interaction with the ball and the decrease of the ball's spin generation, arise from the growing depressions. The deterioration of racket performance during the game, due to the misplacement of strings, subsequent to the first shot of the point played, also stems from these depressions. Moreover, depressions decrease the tensile strength of the longitudinal strings. Ultimately, a high percentage of string breakages occur in the longitudinal strings and, more specifically, at one of the longitudinal depression sites.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to disclose a method to create depressions on the latitudinal strings, which are directional towards the longitudinal strings in the contact points of the two string types. These depressions should be formed, according to this method, by mechanically forcing the rubbing of the latitudinal strings back and forth over the longitudinal strings of strung tennis, squash and badminton rackets, through movement or vibration in the longitudinal axis direction. The friction between the two string types will wear the material at the points of the latitudinal strings which are rubbed over the longitudinal strings. This method will form depressions in the latitudinal strings at these contact points with the longitudinal strings. These depressions will be oriented towards the longitudinal strings—thus their orientation will be alternating along each latitudinal string. Before each shot, the longitudinal strings will mostly remain set in place at the points of latitudinal depressions, owing to an energetic minimum at this position. In this arrangement, depressions will either hold the longitudinal strings in place during the interaction of the racket with the ball, or reduce their movement over the latitudinal strings. This effect will reduce the wear of the longitudinal strings and therefore will contribute to the durability of the racket strings. On the grounds that the latitudinal strings are not prone to tearing due to usage—a formation of depressions of a reasonable depth, will not make the strings significantly more prone to breakage than before. In addition, this effect will cause an application of larger forces on the ball by the longitudinal strings, in the latitudinal strings direction, resulting in a faster spin of the ball. Finally, this method will induce a tendency of the longitudinal strings to remain settled in the latitudinal string depressions during the game, and if nonetheless displaced—to be easily settled back. A dependency on the depth of the depressions formed by this method is evident, and the depression depth in the method is tunable according to the preference. The duration of the movement or vibration can be estimated empirically according to the wear of strings of similar material and similar method application. The method may include the application of additional forces over the strings, which are perpendicular to the plane of the racket strings, in order to accelerate the abrasive process of the latitudinal strings. Mechanical forces applied on the latitudinal strings in the longitudinal strings' axis direction, will run the strings back and forth on the longitudinal strings' direction with perpetual interaction with the longitudinal strings. Similarly, a vibrational motion, applied in the same manner, will cause the formation of equivalent depressions.

It is a core purpose of this invention to disclose a machine which implements the aforementioned method. Said machine may stand as a separate machine or be a part of an assembly which includes the functionality of a stringing machine as well. Said machine, useful for treating strung tennis, squash and badminton rackets for enhancement of string durability, ball-spin generation and ease of string alignment, comprising: (a) At least one string holder capable of moving sideways a latitudinal string on a strung racket; said string holder comprising at least one tooth (in the meaning of protrusion throughout the text) from each side of the string, wherein the back and forth movement of the holder will rub the string against the longitudinal strings. (b) A racket holder useful for setting the racket in place. Said racket holder is interconnected to said string holder directly or via a force generating mechanism. (c) A force generating mechanism, capable of repetitively moving said string holder(s) back and forth in approximately the longitudinal strings direction, wherein said force generating mechanism is interconnected to said string holder.

The aforesaid force generating mechanism may vary in shape and mechanism of action to all the different known mechanisms and methods to generate repeating forces or a vibrational motion. Such mechanisms include, and are not limited to: vibration generating machines or forces generating machines which utilize electrical, electro-mechanical, magnetic, mechanical, electromagnetic or manually powered based apparatuses, which may incorporate magnets or piezoelectric crystals. The operation of the machines can include the conversion of rotary motion of a rotor to linear motion using a motor connected to a cam and a reciprocation follower, a slider-crank mechanism or magnetic, electrical and electromagnetic generated vibrating mechanisms. The force generating mechanism in form of a vibrating agent can also be positioned directly on the string holder or on the shaft which connects it to the base of the machine.

It should be noted that according to the said method and machine, it is possible, but unnecessary, to use the treatment for all the latitudinal strings of the racket in order to receive the desired effect. Most interactions of the ball with the racket occur closer to the center of the strings rather than the frame of the racket, thus the middle strings are more important for this process. Furthermore, in the same latitudinal string, it is more important to carve the depressions in the middle section of the racket rather than close to its edges. Additionally, the pulling of strings away from their position very close to the connection points with the frame, may compromise their durability. In this spirit, it is an object of the current invention to carve the desired depressions in the latitudinal strings with emphasis on the center of the racket's head, rather than its edges and without the need of uniform depression depths across all string crossings.

Treating any partial number of latitudinal strings by said method and machine is possible, and the simultaneous treatment of all latitudinal strings or a partial amount of them with several string holders which are connected to the same force generating mechanism or many force generating mechanisms, is desirable as well. Such a machine should possess several string holders. In addition, the teeth of said holder may appear in a greater number than two. In such a case, the holder will hold the latitudinal string, with the teeth positioned in the spaces between the longitudinal strings in more than one place. The holding places of the latitudinal strings can vary throughout the strings from side to side in the gaps between the crossings with the longitudinal strings, with the emphasis on the center of the racket. The holder's teeth should, preferably, be even and hold the string from both sides of each holding point. Yet the teeth number might also be odd or hold the string from different points, which are not facing each other. For instance, a holder with three teeth, which are, positioned one on the one side of the middle point of the string and both the others on the other side of the string and located 4 cm from the middle point. The teeth of all holders mentioned can be adjustable to different positions and distances from each other. A sequential treatment can be performed over several latitudinal strings as well. Therefore, it is a further intention of the current invention not to be limited in scope by the order, number, holding places or combination of these for the treating of longitudinal strings according to said method and machine. Further, the string holder(s) according to the current invention may be positioned from any side of the racket's plain or even be adjustable to operate on both sides. The holder should move the latitudinal strings sideways, in the longitudinal strings' axis direction, which can be done when the holder is placed from any side while the teeth of the holder are positioned to the sides of the latitudinal strings on the racket's plain. The invention aims to include any other general form and known string holder architecture capable of pulling the string to the sides in a similar manner, as well as any holder embodiments which can be contemplated by a person skilled in the art based on the disclosed description. It should be noted that strung rackets may contain a varying amount of cords which are interweaved to form the desired structure. In some cases, even a single cord is used uncut throughout the racket for both the longitudinal and the latitudinal strings. Therefore, the terms latitudinal string and longitudinal string should be interpreted as the part of the cord stretched between two connection points with the racket.

A specific example of the method is the application of forces parallel to the longitudinal strings, on two points, located ca. 14 cm from each other and symmetrically positioned from both sides of the center point of a latitudinal string in a strung tennis racket. These forces are applied simultaneously or stepwise on each latitudinal string of the racket excluding the four strings closest to the edges. These forces (which can be generated by the disclosed machine) induce a vibrational movement with the amplitude of 0.3 cm and frequency of 10 Hz to the strings. which induces friction between the rubbing points on the latitudinal strings and the few millimeters of the longitudinal strings closest to each point. The process is sustained until depressions of ca. 1.5 mm in depth are formed on the central area of each treated latitudinal string. The longitudinal strings wear is negligible since each point of the latitudinal string is being rubbed over about 0.6 cm of a longitudinal string, therefore, these strings will not wear to any significant depth.

A specific example of said machine, capable of performing the method example, is one including said machine description with a holder featuring four teeth. Said teeth are tuned to hold a latitudinal string of a strung racket, ca. 7 cm from its center, on both sides of the two holding points. The force generating mechanism of this model machine is capable of vibrating the holder in the longitudinal strings' direction with the amplitude of 0.3 cm and frequency of 10 Hz and is connected to said string holder. Said force generating mechanism interconnects the racket holder and the string holder. All three parts of the assembly are a part of a machine that possesses playing rackets stringing machine functionality as well. Said functionality enables the application of a new string to an unstrung tennis racket prior to the application of said method and without the need to disconnect it from the racket holder.

A supplemental feature of the current invention includes the possibility to use said spin and durability improving machine for playing rackets and method thereof to implement depressions on both the latitudinal strings and the longitudinal strings combined. The latitudinal strings depressions will be formed in the same manner as described. By processing the racket in a perpendicular position, and therefore rubbing the longitudinal depressions against the latitudinal depressions, it will be possible to induce depressions on the longitudinal strings as well. These longitudinal depressions will be oriented towards the latitudinal strings and thus the two depression types will interlock the latitudinal strings and longitudinal strings together. By this double depression method, it will be harder for both string types to move when hitting a ball. A moderate depression depth on both string types can induce an increase in the strings durability and spin generation as well.

It is an object of the present invention to provide a method to increase the spin generation capabilities of strung tennis, squash and badminton rackets.

It is an object of the present invention to provide a method for treating strung tennis, squash and badminton rackets, which will increase the strings durability.

It is also an object of the present invention to provide a method for treating strung tennis, squash and badminton rackets in order to decrease longitudinal strings displacement during play, and to make it easier to place these strings back in case of displacements during the game.

It is an object of the present invention to provide a method for the treatment of new and used tennis, squash and badminton rackets, strung with new or used strings, for the improvement of spin generation, string durability and for the lessening of longitudinal string displacement.

It is an object of the present invention to provide a machine intended to increase the spin generation capabilities of strung tennis, squash and badminton rackets.

It is an object of the present invention to provide a machine suitable for the treatment of strung tennis, squash and badminton rackets in order to increase their strings' durability.

It is an object of the present invention to provide a machine for the treating of strung tennis, squash and badminton rackets in order to decrease longitudinal string displacement during play and to make it easier to put these strings back in case of displacements during the game.

It is an object of the present invention to provide a machine for the treatment of new and used tennis, squash and badminton rackets, strung with new or used strings, for the improvement of spin generation, string durability and for lessening of longitudinal string displacement.

It is a core object of the present invention to provide a machine intended to increase the spin generation capabilities of strung tennis, squash and badminton rackets, where said machine possesses the functionality of a racket stringing machine.

It is a core object of the present invention to provide a machine intended for treating strung tennis, squash and badminton rackets in order to increase the strings durability, where said machine possesses the functionality of a racket stringing machine.

It is a core object of the present invention to provide a machine for the treating of strung tennis, squash and badminton rackets, in order to decrease longitudinal string displacement during play and to make it easier to put back these strings in case of displacements during the game, where said machine possesses the functionality of a racket stringing machine.

It is a further object of the present invention to provide a machine for the treatment of new and used tennis, squash and badminton rackets, strung with new or used strings, for the improvement of spin generation, string durability and for lessening of longitudinal strings displacement, where said machine possesses the functionality of a racket stringing machine.

Additional characteristics, features and preferences of the current invention may arise as a consequence of the following claims and the accompanied drawings. Similarly, the functionality of the parts and elements of the structure, as well as their manufacture, will be evident as well. A brief description of the drawings, followed by a detailed one, precede the claims hereafter.

BRIEF DESCRIPTION OF THE FIGURES

The assumed key elements of the spin and durability improving machine for playing rackets and the method thereof according to the present invention, are provided below by way of example. Structural features along with operational methods and objectives will be better deduced considering these figures. Substantial emphasis should be placed on the fact that the drawings are for illustration and clarification purposes only, and are not intended to be a definition of the limits of this invention. In the following figures:

FIGS. 1 to 3 are illustrations of the spin and durability improving machine for playing rackets together with a playing racket sample, wherein: FIGS. 1 and 2 are of different points of view and FIG. 3 is a sectional close up of the racket holder and operating string holder of the machine in FIG. 2;

FIG. 4 is an illustration of a playing racket;

FIG. 5 is a sectional schematic view of a part of two longitudinal strings and two latitudinal strings, which are interweaved together as part of the strings of a playing racket;

FIG. 6 illustrates a sectional close up of the strings of a playing racket while being processed by the spin and durability improving machine for playing rackets in the method described by the current invention;

FIG. 7 corresponds to the result of the process illustrated in FIG. 6 which resulted in the depressions on the latitudinal strings on the rubbing points;

FIG. 8 corresponds to the slightly untangled illustration of the strings in FIG. 7, made for the reason of the latitudinal depressions being visualized better in an unwoven view; and

FIG. 9 is a photograph of the strings of a used tennis racket after the longitudinal strings snapped.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference is now made to FIGS. 1 to 3 that illustrate the structure and operation of the spin and durability improving machine 100 for playing rackets which processes a strung playing racket 200. The aforementioned machine 100 comprises: at least one string holder 110, a racket holder 120 and at least one force generating mechanism 130. The racket, which can represent a tennis racket, a squash racket or a badminton racket for instance, comprises a racket handle 210; a racket frame 220; and two interweaved strings: the longitudinal strings 231, which correspond to the strings that are parallel to the racket handle and the latitudinal strings 232, which are perpendicular to said racket handle 210. The string holder 110 comprises at least one protrusion (tooth) 117, which can be placed besides a string as seen in FIG. 3; a holder frame 113 which can be connected to the teeth directly or to a couple of parallel teeth through a connector 112. Said string holder 110 is connected in FIGS. 1 to 3 to a force generating mechanism 130, through a shaft 111. The aforementioned force generating mechanism includes also a screen 131 and gauges 132 and is interconnected to the racket holder 120. The racket holder includes fasteners 121 which hold the racket in place. As demonstrated in the figures, the teeth of the holder are positioned to the sides of the latitudinal strings of the racket. The movement of said string holder 110, generated by the force generating mechanism 130, causes the connected latitudinal string to move back and forth—rubbing it against the longitudinal strings 231. Maintaining this motion will result gradually in the creation of latitudinal depressions, which are oriented towards the longitudinal strings in the connection points between the two string types. It should be noted that the force generating mechanism stated in this invention is of a general nature and thus can be assembled in several mimicking combinations according to its operating mechanism. Additionally, several string holders, each with several teeth can be used for operating simultaneously on a single racket.

Reference to FIG. 4 which details the different parts of a playing racket 200 of general form, which can be fitted to a tennis racket, a squash racket and a badminton racket. Said racket comprises a racket handle 210, a racket frame 220 and shows in more detail the longitudinal strings 231 and the latitudinal strings 232. Arrows 300 and 390 demonstrate the latitudinal strings axis and longitudinal strings axis directions correspondingly. Plain 333 of the racket is the plain which includes both axes.

FIG. 5 highlights the curvature of a part of two longitudinal strings 231 and two latitudinal strings 232, when strung together in a playing racket 200. New strings, as illustrated, lack depressions on the contact points of the two string types.

FIG. 6 demonstrates the method developed in this invention, whereby forces that are applied on the latitudinal strings 232 by the string holder 110, create a back and forth motion in the direction of the longitudinal axis, as signified by the double-headed arrow 393. The interaction of the teeth 117 of the holder with the strings indicates that it is preferable for these teeth to be close to the string, wrapping it from both sides. The teeth should also hold the string due to their shape and position, for instance being perpendicular to the racket's plain or having a concave curvature to hold the strings. This way, the movement of the string holder will act instantaneously on the string and prevent the string from being damaged or sliding out of the string holder grip. Furthermore, this illustration substantiates the equivalence of the latitudinal strings and the longitudinal strings, which permits the method to work on the longitudinal strings as well for creating longitudinal depressions in addition to latitudinal ones.

In FIG. 7 the longitudinal and latitudinal strings, which were demonstrated earlier in FIG. 5, are now presented subsequent to treatment by the method and machine disclosed in this invention. Latitudinal depressions have been formed in the contact points of the two string types, and the longitudinal strings are now settled inside these depressions.

FIG. 8 displays the longitudinal strings 231 slightly untangled from the latitudinal strings 232 in comparison to FIG. 7, unveiling the latitudinal depressions 999 which were created by the spin and durability improving machine for playing rackets and the method thereof described in this invention. It is evident that when the longitudinal strings are settled in these depressions, their movement capabilities in the latitudinal axis direction is more limited. FIGS. 6 to 8 are drawn not to scale, for illustration purposes.

Lastly, FIG. 9 is a photograph of the strings of a used tennis racket after the longitudinal strings have snapped, without the use of the current method. Normal play depressions are clear evidence of the erosion of the longitudinal strings during usage of this racket. These depressions are scattered along the strings and were positioned at the touching points with the latitudinal strings, before one longitudinal string snapped and caused the longitudinal strings to retreat to the current position.

The present disclosure of the claims will enable a person skilled in the art to utilize and manufacture the present invention. Such a person will recognize that changes may be applied in form and details of the claims without departing from the spirit and scope of the invention. Therefore, the present invention is not intended to be limited to the following disclosure, but to include the scope with all aforementioned changes. 

What is claimed is:
 1. A tennis racket spin and durability improving machine comprising: a. at least one string holder useful for moving a latitudinal string of a strung racket sideways in the longitudinal strings direction, comprising: (i) at least one protrusion (tooth) which can be placed besides a string (ii) a holder frame, said holder frame is interconnected to all said protrusions of the string holder. Said holder frame is interconnected with either the racket holder (b) or the force generating mechanism (c) or both of them (b and c); b. a racket holder useful for setting the racket in place, comprising: at least one racket frame holder of a general form useful for holding the racket directly. Said racket holder is interconnected to said string holder(s) (a) directly or via a force generating mechanism (c); and c. at least one force generating mechanism, of a general form, useful for repetitively moving said string holder(s) back and forth in approximately the longitudinal strings axis direction. Said force generating mechanism is interconnected to said string holder(s) (a).
 2. The machine according to claim 1, wherein the racket holder, string holder and force generation mechanism fit at least one sports racket type from the group of tennis, squash and badminton.
 3. The machine according to claims 1 to 2, wherein said string holder is used for applying additional force in the direction perpendicular to the racket's plain, in a magnitude of up to 5000 N, in order to increase the friction between the latitudinal and longitudinal strings and accelerate the abrasive process.
 4. The machine according to claims 1 to 3, wherein each latitudinal string held by the string holder(s) is applied with maximal force in the longitudinal direction of up to 10,000 N.
 5. The machine according to claims 1 to 4, wherein said machine is combined with a racket stringing machine. Said racket holder is used for both sport racket improving machine and stringing machine functionalities. Such a combined machine comprising at least, additional string tension generating mechanism capable of pulling the strings while stringing the racket and a hinge on which the racket holder can rotate horizontally. The hinge is useful for rotating the racket in order to redirect the racket so that the threaded string will face about the direction of said string tension generating mechanism.
 6. The machine according to claims 1 to 5, wherein the movement of the latitudinal strings over the longitudinal ones is relative, including the movement of the racket by the machine when at list one of the latitudinal strings is held in place.
 7. The machine according to claims 1 to 6, wherein the force generating mechanism is of a general vibrating nature.
 8. The machine according to claims 1 to 7, wherein said sports racket improving machine is connected to a monitor, which measures the friction of the movement of the latitudinal strings over the longitudinal strings using force resistance measurements or vibration relaxation times as a means of indicating the depth of the depressions formed by the machine.
 9. A method of generating depressions on strung sports racket latitudinal strings wherein said method comprising the steps of: a. providing a sports racket; holding a strung racket in place, approximately in the same position; b. applying mechanical forces on at least one latitudinal string in order to rub it back and forth over the longitudinal strings in the contact points; and c. continuing the process until depressions up to 2 mm in depth are formed at any desired part of the latitudinal strings.
 10. The method of claim 9, wherein the movement of the latitudinal strings over the longitudinal ones is relative, including the movement of the racket when at list one of the latitudinal strings is held in place.
 11. The method of claims 9 to 10, wherein the sports racket is a tennis racket or a squash racket or a badminton racket.
 12. The method of claims 9 to 11, useful for creating depressions on both the latitudinal strings and the longitudinal strings. Wherein, providing said machine of claim 5, both the latitudinal and longitudinal strings are treated according to the latitudinal strings' treatment of method
 9. This addition requires the rotation of the racket or the string holder(s) by about 90 degrees in the racket's plain.
 13. A sports racket comprising a strung racket, wherein the latitudinal strings include depressions formed by said method of claim 9
 14. The sports racket of claim 13 wherein said improved sports racket is a tennis or squash or badminton racket. 